UNH News Service: Researchers at the University of New Hampshire used a newly designed device called a skimmer to test samples of foam formed on the top of local waterways for the presence of per- and polyfluoroalkyl substances, or PFAS. Preliminary findings show levels of the so-called forever chemicals were seven to seventy times higher in the foam than levels in the underlying surface water.
“Foam formation on the surface of moving and stagnant water bodies is a natural process and is commonly attributed to organic-rich material, like decaying leaves or algae,” said Paula Mouser, professor of civil and environmental engineering at UNH. “But some contaminants, like PFAS, can act as agents to cause the same looking foam when water mixes with air along shorelines or during high waves. The problem is that it’s hard to determine with the naked eye which foam is harmful because PFAS are odorless and tasteless and they can be stored in the foam at concentrated levels, which may be of concern if humans or animals come in contact with them.”
To help better determine which foams may be hiding the toxic chemicals, the researchers conducted a small pilot study designed to develop and test new methods for sampling and analyzing foams and underlying surface water. The researchers worked directly with community members, who took on the role of citizen scientists, to help determine the location and timing of foam sample collection in the Piscataqua Region Watershed.
In November 2024, samples were collected by boat at three locations in Great Bay and by foot in Rye’s Berry Brook. At each site, foam and surface waters were analyzed for nutrient composition, microbiological community and PFAS. Testing was done at UNH’s Water Quality Lab, UNH Hubbard Center for Genome Studies and Temple University. Results were compared with historic concentrations of PFAS in those areas as well as dissolved organic carbon (DOC) and ammonia (NH4) in the samples. One specific PFAS known as perfluorooctane sulfonic acid (PFOS) was found to be concentrated 24 to 161 times higher in the foam than the water beneath.
“PFAS are found in many consumer products, like plastics and non-stick cookware to cleaning products, and can also be found in electronics and firefighting foams,” said Mouser. “Communities in New Hampshire are working hard to eliminate PFAS from their drinking water and wastewater systems through source reduction and novel water treatment technologies. But we still have much to learn about how these compounds move and where they are ending up in the environment.”
The occurrence of foam in the Piscataqua Region Watershed is of particular interest because it includes the Great Bay Estuarine Reserve and the Hampton-Seabrook Estuary, which support diverse ecosystems and critically important coastal economies. The region also contains legacy PFAS contamination, seven tributaries with discharge from wastewater treatment facilities and many individual and community septic systems that surround the Great Bay.
Foam in watersheds is typically caused by the presence of carbon released from decaying plants, animal and microbial matter. Both carbon and PFAS can act as surfactants—similar to the action of a detergent—lowering the water’s surface tension and allowing bubbles to form easily in turbulent waters. The foam can redissolve back into the water or spread out across the shoreline once the waters calm.
“This was a pilot study and the findings are preliminary but our next steps will be to expand the sample collection to include other areas of the watershed and other estuaries,” said Mouser.
Funding for this work was provided by New Hampshire Sea Grant.
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